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Bycatch Reduction in the Shrimp Fishery
Reduced-Grid Turtle Excluder Device Decreases Bycatch Without Shrimp Loss
Results from a North Carolina Fishery Resource Grant Project
Shrimp Trawling
In 2011, shrimp was North Carolina’s second
most economically valuable fishery. The state’s penaeid
shrimp fishery consists of three species: brown shrimp
(Farfantepenaeus aztecus), white shrimp (Litopenaeus
setiferus) and pink shrimp (F. duorarum). Average annual
landings from 1962 to 2010 were 6.4 million pounds (N.C.
Division of Marine Fisheries, 2012).
The vast majority of shrimpers — about 92 percent — use
otter trawls (NCDMF, 2012) because this gear is effective at
capturing all three shrimp species under most conditions.
However, otter trawls are generally not very selective and often
capture unintended catch, or bycatch, in addition to shrimp
and marketable finfish. Since 1992, federal regulations have
required the shrimp industry to use turtle excluder devices
(TEDs) and bycatch reduction devices in trawls to minimize
encounters with sea turtles and finfish.
The shrimp industry has conducted bycatch reduction
research through gear modification for many years. From an
economic perspective, bycatch can increase a shrimp trawler’s
operating cost because it takes extra fuel to pull heavier nets
and additional time for crew to cull the catch. Large amounts of
bycatch also can crush shrimp, resulting in inferior product.
In the U.S. shrimp fishery, the maximum spacing allowed
between TED grids is 4 inches (TED regulations, 2008). In
2010, John Broome, and Julia and Donna Anderson received
funding from the N.C. Fishery Resource Grant Program to
test a narrower-grid TED. They sought to determine if a 2-inch
reduced-space grid TED could catch shrimp as well as a
traditional 4-inch TED, while reducing bycatch.
Methods
The shrimpers used a 35-foot shrimp trawler with two
identical 42-foot mongoose nets pulled from the stern with a
sled in the middle. One net was equipped with the experimental
2-inch TED and the other had a traditional 4-inch TED. They
collected data from 43 tows in the ocean from one-half mile
north of Carolina Beach Inlet to Lockwood Folly Inlet between
September and December 2010.
Tows lasted approximately 90 minutes. After each tow,
catch from each net was culled individually and the contents
were weighed separately. The researchers recorded the
total weight of bycatch and shrimp, as well as the number of
marketable finfish from each net. Bycatch from each net was
subsampled using one 35-pound shrimp basket and identified
to species when possible.
Before each day’s testing, TEDs were swapped between
nets using a TED zipper, and each tickler chain was measured
in order to maintain the proper setting. At the study’s midpoint,
the nets were swapped in order to eliminate any unknown bias
associated with trawl-door operation. A try net typically fished
from the port side of the vessel was not used during this study
because it could have reduced the catch in the port net.
Gear and Equipment
Two identical 42-foot, 1-and-7/8-inch Spectra mongoose
nets built by Steve Parrish of S&S Trawl Shop in Supply, N.C.,
were used for the tests. New 3/16-inch stainless-steel tickler
chains set 30 inches ahead of the trawl chain line were used.
The fishing vessel was rigged as a stern trawler with two 7-feet
by 3-feet wooden doors with stainless-steel runners and a 6-foot
stainless-steel sled (dummy door). New 5/16-inch stainless-steel
towing cable was installed on the trawl winch. New tongue
BluEprints NORTH CAROLINA SEA GRANT NC State University BOX 8605 RALEIGH, NC 27695-8605
UNC-SG-BP-12-03
This shrimp trawler pulls two otter trawls. Courtesy NCDMF.

Bycatch Reduction in the Shrimp Fishery
Reduced-Grid Turtle Excluder Device Decreases Bycatch Without Shrimp Loss
Results from a North Carolina Fishery Resource Grant Project
Shrimp Trawling
In 2011, shrimp was North Carolina’s second
most economically valuable fishery. The state’s penaeid
shrimp fishery consists of three species: brown shrimp
(Farfantepenaeus aztecus), white shrimp (Litopenaeus
setiferus) and pink shrimp (F. duorarum). Average annual
landings from 1962 to 2010 were 6.4 million pounds (N.C.
Division of Marine Fisheries, 2012).
The vast majority of shrimpers — about 92 percent — use
otter trawls (NCDMF, 2012) because this gear is effective at
capturing all three shrimp species under most conditions.
However, otter trawls are generally not very selective and often
capture unintended catch, or bycatch, in addition to shrimp
and marketable finfish. Since 1992, federal regulations have
required the shrimp industry to use turtle excluder devices
(TEDs) and bycatch reduction devices in trawls to minimize
encounters with sea turtles and finfish.
The shrimp industry has conducted bycatch reduction
research through gear modification for many years. From an
economic perspective, bycatch can increase a shrimp trawler’s
operating cost because it takes extra fuel to pull heavier nets
and additional time for crew to cull the catch. Large amounts of
bycatch also can crush shrimp, resulting in inferior product.
In the U.S. shrimp fishery, the maximum spacing allowed
between TED grids is 4 inches (TED regulations, 2008). In
2010, John Broome, and Julia and Donna Anderson received
funding from the N.C. Fishery Resource Grant Program to
test a narrower-grid TED. They sought to determine if a 2-inch
reduced-space grid TED could catch shrimp as well as a
traditional 4-inch TED, while reducing bycatch.
Methods
The shrimpers used a 35-foot shrimp trawler with two
identical 42-foot mongoose nets pulled from the stern with a
sled in the middle. One net was equipped with the experimental
2-inch TED and the other had a traditional 4-inch TED. They
collected data from 43 tows in the ocean from one-half mile
north of Carolina Beach Inlet to Lockwood Folly Inlet between
September and December 2010.
Tows lasted approximately 90 minutes. After each tow,
catch from each net was culled individually and the contents
were weighed separately. The researchers recorded the
total weight of bycatch and shrimp, as well as the number of
marketable finfish from each net. Bycatch from each net was
subsampled using one 35-pound shrimp basket and identified
to species when possible.
Before each day’s testing, TEDs were swapped between
nets using a TED zipper, and each tickler chain was measured
in order to maintain the proper setting. At the study’s midpoint,
the nets were swapped in order to eliminate any unknown bias
associated with trawl-door operation. A try net typically fished
from the port side of the vessel was not used during this study
because it could have reduced the catch in the port net.
Gear and Equipment
Two identical 42-foot, 1-and-7/8-inch Spectra mongoose
nets built by Steve Parrish of S&S Trawl Shop in Supply, N.C.,
were used for the tests. New 3/16-inch stainless-steel tickler
chains set 30 inches ahead of the trawl chain line were used.
The fishing vessel was rigged as a stern trawler with two 7-feet
by 3-feet wooden doors with stainless-steel runners and a 6-foot
stainless-steel sled (dummy door). New 5/16-inch stainless-steel
towing cable was installed on the trawl winch. New tongue
BluEprints NORTH CAROLINA SEA GRANT NC State University BOX 8605 RALEIGH, NC 27695-8605
UNC-SG-BP-12-03
This shrimp trawler pulls two otter trawls. Courtesy NCDMF.